Effect of structural variation within lipophilic N-(X)sulfonyl carbamoyl lariat ethers on the selectivity and efficiency of competitive alkali metal cation extraction into chloroform

Sixteen lipophilic N-(X)sulfonyl carbamoyl lariat ethers with polyether ring sizes of 12-crown-4, 14-crown-4, 15-crown-5, and 18-crown-6 are utilized for competitive alkali metal cation extractions from aqueous solutions into chloroform. Variation of the electron-withdrawing properties of X in the series of methyl, phenyl, 4-nitrophenyl, and trifluoromethyl allows the influence of the acidity of the C(O)NHSO₂X group in the side arm upon extraction efficiency and selectivity to be assessed. With X = trifluoromethyl, effective alkali metal cation extractions from acidic, neutral, and basic aqueous solutions are achieved. When the crown ether rings are 14-crown-4, 15-crown-5, and 18-crown-6, selectivities for Li⁺, Na⁺, and K⁺, respectively, are observed. Results are compared with those reported for analogous lariat ether carboxylic acids and phosphonic acid monoethyl esters.